Smart Snake Wells in Champion West—Expected and Unexpected Benefits From Smart Completions

Abstract

Snake wells are laterally weaving ("snaking") extended reach horizontal wells that drain a number of vertically stacked, structurally dipping reservoirs. This creates multiple drainage points in each sand and effectively achieves a similar drainage pattern to a multilateral well at a fraction of the cost and technical complexity. The wells are completed with multiple hydraulically controlled interval control valves (ICV) and external casing packers or swellable packers. In addition, the completion includes permanent downhole gauges (PDHG) and distributed temperature sensing (DTS). Seven of these smart snake wells have been successfully drilled in Champion West as of April 2006 and three more are planned during the remainder of 2006. The well design not only facilitates initial clean-up, but is used for reservoir management purposes and to manage gas and water breakthrough. Throughout the well life, variable ICVs are used to achieve equal drawdown along the well bore, leading to a significant increase in reserves by delaying gas breakthrough. In addition, some unexpected benefits materialized from the use of smart completions: In one case, the smart completion enabled the clean-up of the initially uncompleted toe, significantly increasing total recovery from the well. In another case, the smart completion mitigated the risk from a potentially bad cement job, saving a cement repair job or, more likely, a sidetrack. In another well the flexibility of the design enabled the effective shutoff of water bearing zones that were drilled because of slight departures from the planned well trajectory. Through modification of the planned segmentation an expensive re-drill was avoided. The smart snake wells have thus been a key enabler for the economic development of the Champion West field and we expect they will continue to add further value over the lifetime of the wells. Introduction The Champion West field, discovered in 1975, is situated offshore Brunei in a water depth of 40 to 50 m. The area extent of the field is about 12 × 4 km. Although more than 30 wells have been drilled, including a number of appraisal sidetracks, less than 20 percent of the estimated reserves have been produced so far. The field consists of a number of elongated fault blocks. In the vertical sequence each fault is made of multiple, stacked thin sands, interbedded with shale layers. In total, the vertical sequence contains more than 100 individual reservoirs isolated by shale layers.

Smart wells and model-based field production optimization

“…Previously these types of model-based optimization strategies (proactive strategies) were presented in several publications (refer, for instance, (Yeten et al, 2004;Obendrauf et al, 2006;Emerick and Portella, 2007;Chen et al, 2009;van Essen et al, 2010;Su and Oliver, 2010) and showed good results. We do believe that it is difficult and inefficient to implement the aforementioned approaches in full field reservoir models directly, because they would result in large, multidimensional and timeconsuming optimization problems.…”